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Short for Universal Serial Bus. USB is an industry standard for device communication, which allows not only data transfer but also power transfer. In terms of design architecture, USB has a star topology where devices are connected to a port. A single USB port can be used to connect up to 127 peripheral devices, such as mice, modems, and keyboards. This limit arises from the fact that each usb port has a 7-bit address. The port is connected to the device via a cable which, depending on type of device, can have a different. Micro-usb's are normally used in smartphones due to their small size.
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There are three versions of USB devices: USB 1.0; USB 2.0, currently the most used version; and USB 3.0, the latest generation of USB. The speed of data transfer varies from version to version of usb. These speeds are tabulated below:
Version
Speed
1.0
12 Mbit/s
2.0
480 Mbit/s
3.0
5 Gbit/s